U.S. patent number 8,435,148 [Application Number 12/964,545] was granted by the patent office on 2013-05-07 for hydraulic control system for an automatic transmission having electronic transmission range selection with failure mode control.
This patent grant is currently assigned to GM Global Technology Operations LLC. The grantee listed for this patent is Steven P. Moorman. Invention is credited to Steven P. Moorman.
United States Patent |
8,435,148 |
Moorman |
May 7, 2013 |
Hydraulic control system for an automatic transmission having
electronic transmission range selection with failure mode
control
Abstract
A hydraulic control system for a transmission includes a source
of pressurized hydraulic fluid that communicates with an electronic
transmission range selection (ETRS) subsystem. The ETRS subsystem
includes an ETRS valve, a park mechanism, first and second mode
valve assemblies, a latch valve assembly, and a plurality of
solenoids. The ETRS subsystem is configured to provide desired
operating conditions during a plurality of potential failure
conditions.
Inventors: |
Moorman; Steven P. (Dexter,
MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Moorman; Steven P. |
Dexter |
MI |
US |
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Assignee: |
GM Global Technology Operations
LLC (Detroit, MI)
|
Family
ID: |
44257431 |
Appl.
No.: |
12/964,545 |
Filed: |
December 9, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110167812 A1 |
Jul 14, 2011 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61293984 |
Jan 11, 2010 |
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Current U.S.
Class: |
475/116; 475/119;
475/127 |
Current CPC
Class: |
F16H
61/12 (20130101); F16D 48/0206 (20130101); F16H
61/0206 (20130101); F16D 2048/0209 (20130101); F16H
2061/1224 (20130101) |
Current International
Class: |
F16H
61/00 (20060101) |
Field of
Search: |
;475/116,119,127 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO9919644 |
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Mar 2009 |
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WO |
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WO2010028745 |
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Mar 2010 |
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WO |
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Primary Examiner: Estremsky; Sherry
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
No. 61/293,984 filed on Jan. 11, 2010, which is hereby incorporated
in its entirety herein by reference.
Claims
The following is claimed:
1. A hydraulic control system for a transmission, the transmission
having a hydraulically actuated device for engaging a Park mode and
a Drive mode of operation, the transmission having a plurality of
torque transmitting devices selectively engageable to provide at
least one forward speed ratio and at least one reverse speed ratio
when in the Drive mode of operation, the hydraulic control system
comprising: a source for generating a pressurized hydraulic fluid;
a range selection valve in downstream fluid communication with the
source and moveable between at least a first position and a second
position, wherein the pressurized hydraulic fluid is communicated
to the hydraulically actuated device to engage the Drive mode when
the range selection valve is in the second position, and wherein
the pressurized hydraulic fluid is diverted from the hydraulically
actuated device to engage the Park mode when the range selection
valve is in the first position; a first valve in downstream fluid
communication with the source and moveable between at least a first
position and a second position; a second valve in downstream fluid
communication with the first valve and moveable between at least a
first position and a second position; at least one first clutch
actuator in downstream fluid communication with the second valve
and configured to engage one of the torque transmitting devices to
provide the reverse speed ratio upon receipt of the pressurized
hydraulic fluid; at least one second clutch actuator in downstream
fluid communication with the second valve and configured to engage
one of the torque transmitting devices to provide the forward speed
ratio upon receipt of the pressurized hydraulic fluid; a first
drive circuit communicating the pressurized hydraulic fluid from
the first valve to the second clutch actuator and to the range
selection valve to keep the range selection valve in the second
position when the first valve is in the first position and the
second valve is in the second position; a second drive circuit
communicating the pressurized hydraulic fluid from the first valve
to the second clutch actuator and to the range selection valve to
keep the range selection valve in the second position when the
first valve is in the second position and the second valve is in
the first position; and a reverse circuit communicating the
pressurized hydraulic fluid from the first valve to the first
clutch actuator, communicating the pressurized hydraulic fluid from
the first valve to the range selection valve to keep the range
selection valve to the second position, and communicating the
pressurized hydraulic fluid to the first valve to keep the first
valve in the second position when the first valve is in the second
position and the second valve is in the second position.
2. The hydraulic control system of claim 1 further comprising a
latch circuit communicating the pressurized hydraulic fluid from
the first valve through the second valve to an end of the first
valve to keep the second valve from moving before the first valve
when the first valve is in the first position and the second valve
is in the second position.
3. The hydraulic control system of claim 2 further comprising a
latch disable valve in downstream fluid communication with the
source and moveable between at least a first position and a second
position, wherein the pressurized hydraulic fluid is communicated
through the latch disable valve to a second end of the second valve
to move the second valve to the first position when the latch
disable valve is in the first position and wherein the pressurized
hydraulic fluid is prevented from communicating through the latch
disable valve when the latch disable valve is in the second
position.
4. The hydraulic control system of claim 3 further comprising a
second valve solenoid in downstream fluid communication with the
source of pressurized hydraulic fluid, wherein the second valve
solenoid when opened communicates the pressurized hydraulic fluid
to the latch disable valve to move the latch disable valve to the
second position and communicates the pressurized hydraulic fluid to
the second valve to move the second valve to the second
position.
5. The hydraulic control system of claim 1 further comprising a
first valve solenoid in downstream fluid communication with the
source, wherein the first valve solenoid when opened communicates
the pressurized hydraulic fluid to the first valve to move the
first valve to the second position.
6. The hydraulic control system of claim 1 further comprising a
first biasing member in contact with an end of the first valve to
bias the first valve to the first position and further comprising a
second biasing member in contact with an end of the second valve to
bias the second valve to the first position.
7. The hydraulic control system of claim 1 further comprising a
Drive solenoid in downstream fluid communication with the source of
pressurized hydraulic fluid, wherein the Drive solenoid when opened
communicates the pressurized hydraulic fluid to the range selection
valve to move the range selection valve to the second position.
8. The hydraulic control system of claim 1 further comprising a
Park solenoid in downstream fluid communication with the source of
pressurized hydraulic fluid, wherein the Park solenoid when opened
communicates the pressurized hydraulic fluid to the range selection
valve to move the range selection valve to the first position.
9. The hydraulic control system of claim 1 wherein the first drive
circuit further communicates the pressurized hydraulic fluid to a
torque converter control subsystem when the first valve is in the
first position and the second valve is in the second position.
10. The hydraulic control system of claim 1 wherein the second
clutch actuator engages a torque transmitting device that is used
to engage only forward speed ratios.
11. A hydraulic control system for a transmission, the transmission
having a hydraulically actuated device for engaging a Park mode and
a Drive mode of operation, the transmission having a plurality of
torque transmitting devices selectively engageable to provide at
least one forward speed ratio and at least one reverse speed ratio
when in the Drive mode of operation, the hydraulic control system
comprising: a source of pressurized hydraulic fluid; a range
selection valve in downstream fluid communication with the source
of pressurized hydraulic fluid and moveable between at least a
first position and a second position, wherein the range selection
valve when in the second position communicates the hydraulic fluid
to the device in order to engage the Drive mode and wherein the
range selection valve when in the first position prevents the
pressurized hydraulic fluid from communicating to the device in
order to engage the Park mode; a first valve assembly having a
first inlet port in downstream fluid communication with the source
of pressurized hydraulic fluid, a first outlet port, and a second
outlet port, the first valve assembly having a valve moveable
between at least a first position and a second position, wherein
the first inlet port communicates with the first outlet port when
the valve is in the first position and wherein the first inlet port
communicates with the second outlet port when the valve is in the
second position; a second valve assembly having a first inlet port
in downstream fluid communication with second outlet port of the
first valve assembly, a second inlet port in downstream fluid
communication with the first outlet port of the first valve
assembly, a first outlet port in fluid communication with an end of
the range selection valve, and a second outlet port in fluid
communication with an end of the range selection valve, the second
valve assembly having a valve moveable between at least a first
position and a second position, wherein the first inlet port
communicates with the first outlet port when the valve is in the
first position and wherein the second inlet port communicates with
the second outlet port when the valve is in the second position; at
least one first clutch actuator in downstream fluid communication
with the first and second outlet ports of the second valve assembly
and configured to engage one of the torque transmitting devices to
provide the reverse speed ratio upon receipt of the pressurized
hydraulic fluid; and at least one second clutch actuator in
downstream fluid communication with the first and second outlet
ports of the second valve assembly and configured to engage one of
the torque transmitting devices to provide the forward speed ratio
upon receipt of the pressurized hydraulic fluid, wherein the
pressurized hydraulic fluid is communicated from the first valve
assembly to the second clutch actuator and communicated from the
first valve assembly to the range selection valve to bias the range
selection valve to the second position when the valve of the first
valve assembly is in the first position and the valve of the second
valve assembly is in the second position, wherein the pressurized
hydraulic fluid is communicated from the first valve assembly to
the second clutch actuator and communicated from the first valve
assembly to the range selection valve to bias the range selection
valve to the second position when the valve of the first valve
assembly is in the second position and the valve of the second
valve assembly is in the first position, and wherein the
pressurized hydraulic fluid is communicated from the first valve
assembly to the first clutch actuator, communicated from the first
valve assembly to the range selection valve to bias the range
selection valve to the second position, and communicated to an end
of the valve of the first valve assembly to bias the valve of the
first valve assembly to the second position when the valve of the
first valve assembly is in the second position and the second valve
assembly is in the second position.
12. The hydraulic control system of claim 11 wherein the first
valve assembly further includes a second inlet port and a third
outlet port, wherein the second inlet port is in fluid
communication with the third outlet port when the valve of the
first valve assembly is in the first position, and wherein the
second valve assembly includes a third inlet port and a third
outlet port, wherein the third inlet port is in fluid communication
with the third outlet port when the valve of the second valve
assembly is in the second position, and wherein the third outlet
port is in fluid communication with an end of the valve of the
second valve assembly to bias the valve of the second valve
assembly to the second position.
13. The hydraulic control system of claim 12 further comprising a
latch disable valve in downstream fluid communication with the
source of pressurized hydraulic fluid and moveable between at least
a first position and a second position, wherein the pressurized
hydraulic fluid is communicated through the latch disable valve to
a second end of the valve of the second valve assembly to move the
valve of the second valve assembly to the first position when the
latch disable valve is in the first position and wherein the
pressurized hydraulic fluid is prevented from communicating through
the latch disable valve when the latch disable valve is in the
second position.
14. The hydraulic control system of claim 13 further comprising a
second valve solenoid in downstream fluid communication with the
source of pressurized hydraulic fluid, wherein the second valve
solenoid when opened communicates the pressurized hydraulic fluid
to the latch disable valve to move the latch disable valve to the
second position and communicates the pressurized hydraulic fluid to
the valve of the second valve assembly to move the valve of the
second valve assembly to the second position.
15. The hydraulic control system of claim 11 wherein the first
valve assembly further includes a fourth outlet port, wherein the
first inlet port is in fluid communication with the fourth outlet
port when the valve of the first valve assembly is in the first
position, and wherein the fourth outlet port is in fluid
communication with the range selection valve to bias the range
selection valve to the second position.
16. The hydraulic control system of claim 11 further comprising a
first valve solenoid in downstream fluid communication with the
source of pressurized hydraulic fluid, wherein the first valve
solenoid when opened communicates the pressurized hydraulic fluid
to the valve of the first valve assembly to bias the valve of the
first valve assembly to the second position.
17. The hydraulic control system of claim 11 further comprising a
first biasing member in contact with an end of the valve of the
first valve assembly to bias the valve of the first valve assembly
to the first position and further comprising a second biasing
member in contact with an end of the valve of the second valve
assembly to bias the valve of the second valve assembly to the
first position.
18. The hydraulic control system of claim 11 further comprising a
Drive solenoid in downstream fluid communication with the source of
pressurized hydraulic fluid, wherein the Drive solenoid when opened
communicates the pressurized hydraulic fluid to the range selection
valve to bias the range selection valve to the second position.
19. The hydraulic control system of claim 11 further comprising a
Park solenoid in downstream fluid communication with the source of
pressurized hydraulic fluid, wherein the Park solenoid when opened
communicates the pressurized hydraulic fluid to the range selection
valve to bias the range selection valve to the first position.
20. The hydraulic control system of claim 11 wherein the second
clutch actuator engages a torque transmitting device that is used
to engage only forward speed ratios.
Description
TECHNICAL FIELD
The invention relates to a control system for an automatic
transmission, and more particularly to an electro-hydraulic control
system having electronic transmission range selection with failure
mode control.
BACKGROUND
A typical automatic transmission includes a hydraulic control
system that is employed to provide cooling and lubrication to
components within the transmission and to actuate a plurality of
torque transmitting devices. These torque transmitting devices may
be, for example, friction clutches and brakes arranged with gear
sets or in a torque converter. The conventional hydraulic control
system typically includes a main pump that provides a pressurized
fluid, such as oil, to a plurality of valves and solenoids within a
valve body. The main pump is driven by the engine of the motor
vehicle. The valves and solenoids are operable to direct the
pressurized hydraulic fluid through a hydraulic fluid circuit to
various subsystems including lubrication subsystems, cooler
subsystems, torque converter clutch control subsystems, and shift
actuator subsystems that include actuators that engage the torque
transmitting devices. The pressurized hydraulic fluid delivered to
the shift actuators is used to engage or disengage the torque
transmitting devices in order to obtain different gear ratios.
While previous hydraulic control systems are useful for their
intended purpose, the need for new and improved hydraulic control
system configurations within transmissions which exhibit improved
performance, especially from the standpoints of efficiency,
responsiveness and smoothness, is essentially constant.
Accordingly, there is a need for an improved, cost-effective
hydraulic control system for use in a hydraulically actuated
automatic transmission.
SUMMARY
A hydraulic control system for a transmission is provided. The
hydraulic control system includes a source of pressurized hydraulic
fluid that communicates with an electronic transmission range
selection (ETRS) subsystem. The ETRS subsystem includes an ETRS
valve, a park mechanism, first and second mode valve assemblies, a
latch valve assembly, and a plurality of solenoids. The ETRS
subsystem is configured to provide desired operating conditions
during a plurality of potential failure conditions.
Further features, aspects and advantages of the present invention
will become apparent by reference to the following description and
appended drawings wherein like reference numbers refer to the same
component, element or feature.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings described herein are for illustration purposes only
and are not intended to limit the scope of the present disclosure
in any way.
FIGS. 1A-1D are diagrams of a hydraulic control system according to
the principles of the present invention.
DESCRIPTION
With combined reference to FIGS. 1A-1D, a hydraulic control system
according to the principles of the present invention is generally
indicated by reference number 100. The hydraulic control system 100
is operable to control torque transmitting mechanisms, such as
synchronizers, clutches, and brakes within a transmission, as we as
providing lubrication and cooling to components within the
transmission and to control a torque converter coupled to the
transmission. The hydraulic control system 100 includes a plurality
of interconnected or hydraulically communicating subsystems
including a pressure regulator subsystem 102, a torque converter
control subsystem 104, a cooler flow subsystem 106, a lubrication
control subsystem 108, an electronic transmission range selection
(ETRS) control subsystem 110, and a clutch control subsystem
112
With reference to FIG. 1A, the pressure regulator subsystem 102 is
operable to provide and regulate pressurized hydraulic fluid 113,
such as oil, throughout the hydraulic control system 100. The
pressure regulator subsystem 102 draws hydraulic fluid 113 from a
sump 114. The sump 114 is a tank or reservoir preferably disposed
at the bottom of a transmission housing to which the hydraulic
fluid 113 returns and collects from various components and regions
of the transmission. The hydraulic fluid 113 is forced from the
sump 114 and communicated through a sump filter 116 and throughout
the hydraulic control system 100 via a pump 118. The pump 118 is
preferably driven by an engine (not shown) and may be, for example,
a gear pump, a vane pump, a gerotor pump, or any other positive
displacement pump. The pump 118 includes an inlet port 120 and an
outlet port 122. The inlet port 120 communicates with the sump 114
via a fluid line 124. The outlet port 122 communicates pressurized
hydraulic fluid 113 to a fluid line 126. The fluid line 126 is in
communication with a spring biased one-way valve 128, a spring
biased blow-off safety valve 130, and a pressure regulator valve
132. The one-way valve 128 is used to selectively prevent hydraulic
flow into the main pump 118 when the main pump 118 is
non-operational. The safety valve 130 is set at a relatively high
predetermined pressure and if the pressure of the hydraulic fluid
in the fluid line 126 exceeds this pressure, the safety valve 128
opens momentarily to relieve and reduce the pressure of the
hydraulic fluid.
The pressure regulator valve assembly 132 includes ports 132A-G.
Port 132A is in communication with fluid line 126. Port 132B is an
exhaust port that communicates with the sump 114. Port 132C is in
communication with a fluid line 134 that communicates with fluid
line 124 (i.e. feeds back into the inlet port 120 of the pump 118).
Port 132D is in communication with fluid line 126. Fluid port 132E
is in communication with a fluid line 136 and via a flow
restriction orifice 138 with a fluid line 140. Fluid port 132F is
in communication with the fluid line 140. Fluid line 140
trifurcates into at least three parallel branches 140A, 140B, and
140C each having located therein variously sized flow restriction
orifices 141A, 141B, and 141C, respectively, shown in FIG. 1B.
Finally, port 132G is in communication with a fluid line 142.
The pressure regulator valve assembly 132 further includes a valve
144 slidably disposed within a bore 146. The valve 144
automatically changes position to dump excess flow from fluid line
126 until a pressure balance is achieved between the commanded
pressure and the actual pressure. The valve 144 is modulated by a
variable bleed solenoid 148 that communicates with fluid line 142.
For example, the solenoid 148 commands a fluid pressure by sending
pressurized hydraulic fluid to port 132G to act on the valve 144.
Simultaneously, fluid pressure from fluid line 126 enters port 132A
and acts on the opposite side of the valve 144. Pressure balance
between the commanded pressure from the solenoid 148 and pressure
within line 126 is achieved as the valve 144 moves and allows
selective communication between port 132D and port 132C, thereby
bleeding pressure from fluid line 126.
Fluid line 126 also communicates downstream of the pressure
regulator valve assembly 132 with a one-way valve 150. The one-way
valve 150 allows fluid communication from fluid line 126 to a fluid
line 152 and prevents fluid communication from fluid line 152 to
fluid line 126. Fluid line 152 communicates with a feed limit valve
assembly 154.
The feed limit valve assembly 154 limits the maximum pressure of
hydraulic fluid to the torque converter control subsystem 104, the
cooler control subsystem 106 as well as various control solenoids,
as will be described below. The feed limit valve assembly 154
includes ports 154A-F. Ports 154C and 154F are in communication
fluid line 136 and therefore port 132E of the pressure regulator
valve 132. Port 154D is in communication with fluid line 152. Ports
154A, 154B, and 154E are exhaust ports that communicate with the
sump 114.
The feed limit valve assembly 154 further includes a valve 156
slidably disposed within a bore 158. The valve 156 automatically
changes position to reduce flow from fluid line 152 (i.e. line
pressure from the pump 118) to fluid line 136. For example, the
valve 156 is biased to a first position by a spring 160. In the
first position, at least a partial flow of fluid from line 152
communicates from port 154D through the feed limit valve assembly
154 to port 154C and then to fluid line 136. As the pressure within
fluid line 136 increases, feedback pressure acting on the valve 156
via port 154F moves the valve 156 against the spring 160, thereby
further reducing the pressure of the hydraulic fluid within fluid
line 136, until a pressure balance is achieved on the valve 156. By
controlling the pressure to fluid line 136 which communicates
through the pressure regulator valve 132 to fluid line 140, the
feed limit valve 154 controls the maximum pressure feeding the TCC
control subsystem 104 and the lubrication control subsystem
108.
The pressure regulator subsystem 102 further includes an alternate
source of hydraulic fluid that includes an auxiliary pump 170. The
auxiliary pump 170 is preferably driven by an electric engine,
battery, or other prime mover (not shown) and may be, for example,
a gear pump, a vane pump, a gerotor pump, or any other positive
displacement pump. The auxiliary pump 170 includes an inlet port
172 and an outlet port 174. The inlet port 172 communicates with
the sump 114 via a fluid line 176. The outlet port 174 communicates
pressurized hydraulic fluid to a fluid line 178. The fluid line 178
is in communication with a spring biased blow-off safety valve 180
and a one-way valve 182. The safety valve 180 is used to relieve
excess pressure in fluid line 178 from the auxiliary pump 170. The
one-way valve 182 is in communication with fluid line 152 and is
operable to allow hydraulic fluid flow from fluid line 178 to fluid
line 152 and prevent hydraulic fluid flow from fluid line 152 to
fluid line 178. Therefore, during normal operating conditions,
fluid flow from the pump 118 is prevented from backfilling the
auxiliary pump 170 by the one-way valve 182. During high efficiency
modes of operation when the engine, and therefore the pump 118, are
inactive, and the auxiliary pump 170 is engaged, fluid flow from
the auxiliary pump 170 is prevented from backfilling the pump 118
by the one-way valve 150.
With specific reference to FIG. 1B, the TCC subsystem 104 receives
pressurized hydraulic fluid from the feed limit valve assembly 154
and the pressure regulator valve assembly 132 via fluid line 140.
The TCC subsystem 104 includes a TCC control valve 184 and a
solenoid 186 that modulates pressure to a torque converter 188 and
a torque converter clutch 189.
The TCC control valve assembly 184 includes ports 184A-M. Ports
184A and 184B are exhaust ports that communicate with the sump 114.
Ports 184I, 184J, and 184K are each in communication with branches
140A, 140B, and 140C of fluid line 140, respectively. Port 184C
communicates with a fluid line 185. Fluid line 185 communicates
with a TCC control valve pressure switch 190. Port 184D
communicates with a branch 140D of fluid line 140. Port 184E
communicates with a safety blow-off valve 192 that release
pressurized hydraulic fluid when the torque converter 188 is on or
engaged. Port 184F communicates with the torque converter 188 via a
fluid line 191. Ports 184G and 184L communicate with a fluid line
196. Port 184H communicates with the torque converter 188 via a
fluid line 193. Finally, port 184M communicates with a fluid line
198. Fluid line 198 communicates with the solenoid 186 and with the
torque converter 188. The solenoid 186 is preferably a high flow,
direct acting variable force solenoid, though other types of
actuating devices may be employed without departing from the scope
of the present disclosure. The solenoid 186 is operable to engage
the torque converter clutch 189 via a clutch actuator 187.
The TCC control valve assembly 184 further includes a valve 200
slidably disposed within a bore 202. The valve 200 is actuated by
the solenoid 186 that actuates the valve 200 against a spring 204.
In a first position with the valve 200 not shifted against the
spring 204 (i.e. a de-stroked position), hydraulic fluid from fluid
line 140 is directed through the branches 140A-B and orifices
141A-B to ports 184I and 184J, through the valve assembly 184 to
port 184H, and then to the torque converter 188. The output of the
torque converter 188 communicates through line 191 to port 184F of
the TCC control valve assembly 184, from port 184F to port 184G and
on to the cooler control subsystem 106. The valve 200 is shifted
against the spring by activation of the solenoid 186. As pressure
of the hydraulic fluid acting on the valve 200 from port 184M via
the solenoid 186 increases, a threshold is crossed where the valve
200 is shifted against the spring 204. As the valve 200 shifts,
hydraulic fluid from fluid line 140 is directed through the
branches 140A-C and orifices 141A-C, thereby controlling the rate
of hydraulic fluid flow to port 184H and therefore the rate of
hydraulic fluid flow to the torque converter 188. For example, as
the valve 200 shifts, port 184K communicates with port 184L,
thereby bleeding off flow from fluid line 140 to fluid line 196,
and port 184J closes thereby further reducing the fluid flow to
port 184H. As the valve 200 shifts completely against the spring
204, the valve 200 diverts the output from the torque converter 188
via port 184F to port 184E such that the hydraulic fluid leaving
the torque converter 188 returns to the sump 114 via the blow-off
valve 192. Accordingly, the TCC control valve 184 controls the flow
rate of hydraulic fluid to the torque converter 188 and to the oil
cooler subsystem 106.
The cooler control subsystem 106 includes an oil cooler 210 and a
fine micron oil filter 212. The oil cooler 210 is in communication
with fluid line 196. The oil filter 212 is in communication with
the oil cooler 210 and with a fluid line 214. Fluid line 214
includes three branches 214A-C that communicate with the
lubrication control subsystem 108 and a fourth branch 214D that
communicates with a spring biased one-way valve 216. Branch 214C
includes a flow restricting orifice 215, or override orifice, used
to control fluid flow through the lubrication subsystem 108, as
will be described in greater detail below. The one-way valve 216
communicates with fluid line 185. If the pressure of the hydraulic
fluid in the fluid line 214D exceeds a pressure threshold, the
one-way valve 216 opens momentarily to relieve and reduce the
pressure of the hydraulic fluid within fluid line 214D. The cooler
control subsystem 106 further includes a spring biased blow-off
safety valve 218 disposed either in parallel with the oil filter
210 or integrated within the oil filter 210 that allows hydraulic
fluid to bypass the oil filter 210 in the event of inadequate
cooler flow. The blow-off valve 218 is set at a predetermined
pressure and if the pressure of the hydraulic fluid in the fluid
line 196 exceeds this pressure, the blow-off valve 218 opens
momentarily to increase the flow of hydraulic fluid from the cooler
flow subsystem 106.
The lubrication control subsystem 108 regulates lubrication fluid
pressure as a function of line pressure delivered from the pump 118
or auxiliary pump 170. Hydraulic fluid regulated by the lubrication
control subsystem 108 lubricates and cools the various moving parts
of the transmission and provides the source of hydraulic fluid for
filling a clutch centrifugal compensator. The lubrication control
subsystem 108 receives hydraulic fluid from the cooler flow
subsystem 106 via fluid line 214.
The lubrication control subsystem 108 includes a lubrication
regulator valve assembly 220 and a ball check valve 221. The ball
check valve 221 includes three ports 221A-C. The ball check valve
221 closes off whichever of the ports 221A and 221B that is
delivering the lower hydraulic pressure and provides communication
between whichever of the ports 221A and 221B having or delivering
the higher hydraulic pressure and the outlet port 221C.
The lubrication regulator valve assembly 220 includes ports 220A-L.
Port 220A communicates with fluid line 126 and therefore receives
line pressure from the pump 118. Port 220B communicates with a
fluid line 222. Fluid line 222 includes two branches 222A and 222B.
Branch 222A communicates with the ETRS subsystem 110 and branch
222B communicates with port 221B of the ball check valve 221. Ports
220C and 220L are exhaust ports that communicate with the sump 114.
Port 220D communicates with fluid line 214A. Ports 220E and 220H
communicate with a fluid line 224. Fluid line 224 includes a branch
224A that communicates with port 221A of the ball check valve 221.
Ports 220I and 220J communicate with fluid line 140 and with a
pressure switch 226. Finally, port 220K communicates with port 221C
of the ball check valve 221.
The lubrication regulator valve assembly 220 further includes a
valve 228 slidably disposed within a bore 230. The valve has a
first end and a second end. The valve 228 has three functional
positions: a basic regulating position shown in FIG. 2A, a
supplemental regulating position shown in FIG. 2B, and an override
position shown in FIG. 2C. The valve 228 is moved between the
positions based on a balance of forces acting on each of the first
end and the second end of the valve 228. The basic regulating
position provides an output pressure via fluid line 224 that is
proportional to the line pressure (i.e. the pressure in fluid line
126). In the basic regulating position, line pressure via fluid
line 126 enters port 220A and acts on an end of the valve 228
against the bias of a spring 235. As the valve 228 strokes against
the spring 235, port 220F communicates with port 220E. Accordingly,
hydraulic fluid flow from the cooler subsystem 106 communicates
from fluid line 214B to port 220F, through the valve 228, and out
fluid port 220E to fluid line 224. Feedback pressure from fluid
line 224 communicates through branch 224A, through the ball check
valve 221, and into the valve assembly 220. The hydraulic fluid
acts on the valve 228 and creates a balancing force against the
line pressure which keeps the valve 228 in a position to regulate
the fluid flow to fluid line 224. In addition, ports 220I, 220J,
220C, and 220G are isolated by the valve 228, which in turn keeps
the fluid pressure within fluid line 140 high which in turn allows
the pressure switch 226 to sense a high pressure thereby indicating
that the valve 228 is regulating fluid flow to fluid line 224.
If the fluid flow from the cooler subsystem 106 drops sufficiently,
the line pressure acting on the valve 228 from fluid line 126 will
move the valve 228 to the supplemental or stroked position. In the
supplemental position, not only is fluid flow from the cooler
subsystem 106 increased by opening port 220F to port 220E, but in
addition port 220I is allowed to communicate with fluid port 220H.
Accordingly, fluid flow from the feed limit valve 154 is
communicated to the lubrication control valve 220 via fluid line
140, thereby increasing the fluid flow to fluid line 224. A flow
restriction orifice 237 in fluid line 140 limits the flow of
hydraulic fluid to the lubrication control valve 220.
Finally, the override position is achieved by activating a solenoid
240 (see FIG. 1C) that is in communication with fluid line 222A.
The override position is activated during low line pressures (i.e.
when the pump 118 is operating at a reduced speed due to engine
idling). Solenoid 240 is an on/off solenoid that is multiplexed
with the ETRS subsystem 110, as will be described in greater detail
below. The hydraulic fluid flow from the solenoid 240, when
activated, communicates with the ball check valve 221 via fluid
line 222A. The ball check valve 221 prevents the fluid flow from
the solenoid 240 from entering fluid line 224. As the fluid flow
from the solenoid 240 enters port 220K, the hydraulic fluid
contacts the valve 228 and, along with the spring 235, moves the
valve to a de-stroked position. In the override position, port 220F
is isolated from port 220E. However, port 220G is allowed to
communicate with port 220H. Fluid flow from the cooler subsystem
106 via fluid line 214C is reduced by the relatively narrow
override orifice 215. In addition, port 220D, previously isolated,
is allowed to communicate with port 220C. Therefore, fluid flow
from the cooler subsystem 106 is further reduced as fluid flow is
diverted through branch 214A to port 220D, from port 220D to port
220C, and out port 220A to the sump 114. Finally, port 220J is
allowed to communicate with port 220L, thereby allowing the fluid
flow from the feed limit valve 154 via fluid line 140 to exhaust to
the sump 114. However, due to gasket slots 243 positioned upstream
of the pressure switch 226, the pressure between the pressure
switch 226 and the exhaust port 220L drops. The drop in pressure
sensed by the pressure switch 226 confirms that the valve 228 is in
the override position. The override position greatly reduces the
flow of hydraulic fluid to fluid line 224 and therefore to the
components of the transmission, thereby reducing the parasitic spin
loss. The override position is used under low power generation
conditions, such as engine idle.
The lubrication regulator valve pressure switch 226 and the TCC
control valve pressure switch 190 cooperate to diagnose a stuck
pressure regulator valve assembly 132 or a stuck feed limit valve
assembly 154. A non-pressurized state is assigned to the TCC
applied position of the TCC control valve assembly 184 and to the
lubrication override position of the lubrication valve assembly
220. Both pressure switches 226, 190 are fed with hydraulic fluid
pressurized by the feed limit valve assembly 154. Depending on the
commanded state of the valve assemblies 184, 220, both pressure
switches 226, 190 indicating no pressure can be used as a
diagnostic signal.
Returning to FIG. 1C, and with continued reference to FIGS. 1A and
1B, the ETRS control subsystem 110 will now be described. The ETRS
control subsystem 110 uses line pressure hydraulic fluid from the
pump 118 or the auxiliary pump 170 via fluid line 152 to engage a
range selection via the clutch actuator subsystem 112. The ETRS
control subsystem 110 is controlled using the hydraulic fluid from
the feed limit control valve assembly 154 via fluid line 136. The
ETRS control subsystem 110 includes previously described solenoid
240 as well as three additional solenoids 242, 244, and 246. Each
of the solenoids 240, 242, 244, 246 are normally low, on-off
solenoids that are each supplied with hydraulic fluid via fluid
line 136. Fluid line 136 further provides hydraulic fluid to
solenoid 148 (FIG. 1A). The solenoids 240, 242, 244, and 246 are
used to actuate an ETRS valve assembly 250, a latch disable valve
assembly 252, and first and second mode valve assemblies 254,
256.
The ETRS valve assembly 250 includes ports 250A-H. Port 250A
communicates with fluid line 222A. Port 250B communicates with a
fluid line 260. Port 250C communicates with a fluid line 262. Port
250D communicates with fluid line 152. Port 250E communicates with
a fluid line 264. Port 250F communicates with a fluid line 266.
Fluid line 266 communicates with solenoid 242. Port 250G is a one
way exhaust port that communicates with the sump 114 which is used
to improve the response time for the ETRS valve assembly 250 to
de-stroke during a return to Park under extreme cold operating
conditions. Finally, port 250H is an exhaust port that communicates
with the sump 114.
The ETRS valve assembly 250 further includes a valve 268 slidably
disposed within a bore 270. The valve 268 is actuated to a stroked
position or out-of-Park position by the solenoid 240 and by
hydraulic fluid acting on valve 268 delivered via fluid line 262
and to a de-stroked position or Park position by a spring 272 and
by hydraulic fluid acting on the valve 268 delivered via fluid line
266. In the out-of-Park position, solenoid 240 is opened and fluid
from line 222A contacts the valve 268 and moves the valve 268
against the spring 272. In addition, fluid from line 262 which is
sourced by line pressure via the mode valves 254 and 256 and fluid
line 152, contacts the valve 268 to stroke the valve. In this
condition, port 250D communicates with port 250E. Accordingly, line
pressure hydraulic fluid from fluid line 152 communicates to port
250D, from port 250D through the ETRS valve assembly 250 to port
250E, and from port 250E to fluid line 264. Fluid line 264
communicates with a Park servo assembly 276. The hydraulic fluid
enters the Park servo assembly 276. The Park servo assembly 276
includes a piston 278 that moves upon contact by the hydraulic
fluid, thereby mechanically disengaging a Park system (not shown).
A Park inhibit solenoid assembly 281 is connected to the Park servo
assembly 276. The Park inhibit solenoid assembly 281 a mechanical
latching solenoid to hold the system out of Park if an operator
wishes to have the vehicle mobile with the engine off. The Park
inhibit solenoid assembly 281 also preferably includes two position
switches, one mechanical and one Hall-effect, that confirm the
position of the Park system to the engine controller and
transmission controller to be used for diagnostic purposes.
In the Park position, solenoid 240 is closed and solenoid 242 is
opened and the valve 268 is de-stroked by the spring 272 and by
hydraulic fluid delivered from the solenoid 242 via line 266. In
this position, port 250E communicates with port 250H and the Park
servo assembly 276 exhausts, thereby engaging the Park system. The
valve 268 is configured such that the spring 272 and hydraulic
fluid from solenoid 242 will overcome the forces exerted on the
valve 268 by any one of hydraulic fluid delivered by solenoid 240
and hydraulic fluid delivered via fluid line 262. If both sources
of hydraulic fluid are present, the forces exerted on the valve 268
by hydraulic fluid from the solenoid 240 and hydraulic fluid
delivered via fluid line 262 will overcome forces exerted on the
valve 268 by the spring 272 and by hydraulic fluid from solenoid
242, thereby assuring a failed signal can be overcome. The Park
controls are configured so that if all hydraulic pressure is lost
in the hydraulic control system 100, the Park system is
engaged.
The first mode valve assembly 254 includes ports 254A-K. Port 254A
communicates with a fluid line 280. Port 254B communicates with a
fluid line 282. Port 254C communicates with fluid line 152. Port
254D communicates with a fluid line 284. Port 254E communicates
with a fluid line 286. Port 254F and 254J are exhaust ports that
communicate with the sump 114. Port 254G communicates with a fluid
line 288. Port 254H communicates with a fluid line 290. Port 254I
communicates with a branch 137 of fluid line 136. Branch 137
communicates with solenoid 244 and with fluid line 136 via flow
orifices 291. Port 254K communicates with fluid line 136 via a flow
orifice 296.
The first mode valve assembly 254 further includes a valve 292
slidably disposed within a bore 293. The valve 292 is actuated by
the solenoid 244 and a spring 294. When solenoid 244 is opened,
fluid from line 136 communicates through solenoid 244 and moves the
valve 292 against the spring 294. Accordingly, the valve 292 is
moveable between a stroked position where the spring 294 is
compressed and a de-stroked position, shown in FIG. 1C. Also acting
against the spring 294 is the reverse oil (i.e. the hydraulic fluid
used to initiate a reverse gear state) delivered to port 254H
communicated via fluid line 290, the second mode valve assembly
256, fluid line 286, and fluid line 284 from the ETRS valve
assembly 250. Acting with the spring 294 on the valve 292 is either
out of park oil or return to park oil communicated via fluid line
280 from the ETRS valve assembly 250. In the stroked position,
solenoid 244 is opened and fluid from line 137 contacts the valve
292 and moves the valve 292 against the spring 294. In this
condition, port 254B communicates with port 254J and exhausts,
ports 254C and 254D communicate with port 254E, port 254G
communicates with port 254F and exhausts, and port 254K is
closed.
In the de-stroked position, solenoid 244 is closed and the valve
292 is positioned by the spring 294 and hydraulic fluid via line
280. In this position, port 254B communicates with port 254C, ports
254E and 254D communicate with port 254F and exhaust, and port 254G
communicates with port 254K. Accordingly, by stroking and
de-stroking the valve 292, hydraulic fluid is diverted between
fluid lines 282, 288 and fluid line 286.
The latch valve assembly 252 generally includes ports 252A-E. Ports
252A and 252B are exhaust ports that communicate with the sump 114.
Port 252C communicates with a fluid line 300. Port 252D
communicates with fluid line 280. Port 252E communicates with a
fluid line 301 that in turn communicates with solenoid 246. The
latch valve assembly 252 includes a valve 303 slidably disposed
within a bore 305. The valve 303 is actuated by the solenoid 246
and a spring 307. When solenoid 246 is opened, fluid from line 136
communicates through solenoid 246 and line 301 and moves the valve
303 against the spring 307. The valve 303 is moveable between a
stroked position where the spring 307 is compressed, shown in FIG.
1C, and a de-stroked position where the spring 307 is not
compressed. In the stroked position, port 252C communicates with
port 252B and exhausts and port 252D is blocked. In the de-stroked
position, port 252C communicates with port 252D. The latch valve
assembly 252 is operable to latch or engage the second mode valve
assembly 256. As will be described in greater detail below, the
latch valve assembly 252 is used to override the position of the
second mode valve assembly 256.
A ball check valve 309 is disposed between the ETRS valve 250 and
the latch valve 252. The ball check valve 309 includes three ports
309A-C. Port 309A communicates with fluid line 260. Port 309B
communicates with fluid line 266. Port 309C communicates with fluid
line 280. The ball check valve 309 closes off whichever of the
ports 309A and 309B that is delivering the lower hydraulic pressure
and provides communication between whichever of the ports 309A and
309B having or delivering the higher hydraulic pressure and the
outlet port 309C.
The second mode valve assembly 256 includes ports 256A-N. Ports
256A, 256D, 256J, and 256M are exhaust ports that communicate with
the sump 114. Port 256B communicates with fluid line 300. Ports
256C and 256G communicate with a fluid line 302. Port 256E
communicates with fluid line 290. Port 256F communicates with fluid
line 286. Port 256H communicates with fluid line 282. Port 256I
communicates with fluid line 311 that feeds solenoid 186. Port 256K
communicates with fluid line 288. Port 256L communicates with a
fluid line 306. Port 256N communicates with a fluid line 308.
The second mode valve assembly 256 further includes a valve 310
slidably disposed within a bore 312. The valve 310 is actuated by
the solenoid 246 via the latch valve 252 and a spring 314 or
directly through fluid line 301 and ball check valve 320. The valve
310 is moveable between a stroked position where the spring 314 is
compressed, shown in FIG. 2B, and a de-stroked position. When
solenoid 246 is opened, hydraulic fluid is communicated via line
301 to both the second mode valve assembly 256 and the latch valve
assembly 252. The fluid communicated to the latch valve assembly
252 moves the valve 303 to its stroked position, thereby allowing
communication from the solenoids 240 and 242 to the spring side of
the valve 310 of the second mode valve assembly 256. If either
solenoids 240 or 242 are opened (i.e. activating an out-of-Park or
return to Park condition), hydraulic fluid communicates through
ball check valve 309, to line 280, through the latch valve assembly
252, and to the second mode valve assembly 256 via line 300. This
hydraulic fluid then keeps the valve 310 in the second position. If
no fluid from solenoids 240 and 242 contact valve 310, the
hydraulic fluid communicated from solenoid 246 moves the valve 310
to its stroked position.
In the stroked position, port 256C communicates with port 256D and
exhausts, port 256E communicates with port 256F, port 256G is
blocked, port 256I communicates with port 256H, port 256J is
blocked, port 256L communicates with port 256K, and port 256M is
blocked. In the de-stroked position, port 256C is blocked, port
256E communicates with port 256D and exhausts, port 256G
communicates with port 256F, port 256H is blocked, port 256I
communicates with port 256J and exhausts, port 256K is blocked, and
port 256L communicates with port 256M and exhausts.
A latch oil circuit is fed pressurized hydraulic fluid by fluid
line 136 and is defined by fluid line 288, fluid line 306, a ball
check valve 320, and fluid line 308. The ball check valve 320
includes three ports 320A-C. Port 320A communicates with fluid line
301. Port 320B communicates with fluid line 306. Port 320C
communicates with fluid line 308. The ball check valve 320 closes
off whichever of the ports 320A and 320B that is delivering the
lower hydraulic pressure and provides communication between
whichever of the ports 320A and 320B having or delivering the
higher hydraulic pressure and the outlet port 320C. Pressurized
hydraulic fluid is communicated through the latch oil circuit from
line 136 when the first mode valve assembly 254 is in the
de-stroked position and the second mode valve assembly 256 is in
the stroked position. The pressurized hydraulic fluid communicates
from line 136 through the first mode valve assembly 254, through
line 288, through the second mode valve assembly 256, through line
306, through the ball check valve 320, and through line 308 to act
on the valve 310.
With reference to FIG. 1D and continued reference to FIG. 1C, the
clutch control subsystem 112 provides hydraulic fluid to clutch
actuators 330A-E. The clutch actuators 330A-E are hydraulically
actuated pistons that each engage one of the plurality of torque
transmitting devices to achieve various speed ratios. Clutch
actuator 330E includes two apply areas 330Ea and 330Eb. Each of the
clutch actuators 330A-E are controlled by a variable force solenoid
332A-F, with clutch actuator 330E controlled by two variable force
solenoids 332E and 332F. This separate control of clutch actuator
330E provides maximum flexibility to tailor clutch torque
characteristics to a wide range of high torque and low torque
shifting conditions.
Solenoid 332A is in communication with a fluid line 334 and with a
fluid line 336. Fluid line 334 communicates with a ball check valve
338. The ball check valve 338 includes three ports 338A-C. Port
338A communicates with fluid line 290. Port 338B communicates with
a fluid line 340. Port 338C communicates with fluid line 334. The
ball check valve 338 closes off whichever of the ports 338A and
338B that is delivering the lower hydraulic pressure and provides
communication between whichever of the ports 338A and 338B having
or delivering the higher hydraulic pressure and the outlet port
338C. Therefore, solenoid 332A is fed hydraulic fluid through the
mode valves 254, 256 from fluid line 152 (i.e. by either drive oil
or reverse oil and therefore can only be pressurized when the mode
valves 254, 256 are positioned in the Drive or Reverse
arrangement). Accordingly, an unintended gear engagement in Neutral
if a clutch solenoid fails to a high pressure is prevented. Fluid
line 336 delivers hydraulic fluid from the solenoid 332A to the
shift actuator 330A.
Solenoid 332B is in communication with fluid line 340 and a fluid
line 342. Fluid line 340 communicates with a ball check valve 344.
The ball check valve 344 includes three ports 344A-C. Port 344A
communicates with fluid line 302. Port 344B communicates with fluid
line 311. Port 344C communicates with fluid line 340. The ball
check valve 344 closes off whichever of the ports 344A and 344B
that is delivering the lower hydraulic pressure and provides
communication between whichever of the ports 344A and 344B having
or delivering the higher hydraulic pressure and the outlet port
344C. Therefore, solenoid 332B is fed hydraulic fluid through the
mode valves 254, 256 from fluid line 152 (i.e. by the drive oil and
therefore can only be pressurized when the mode valves 254, 256 are
positioned in the Drive arrangement). Fluid line 342 delivers
hydraulic fluid from the solenoid 332B to the shift actuator
330B.
Solenoid 332C is in communication with fluid line 340 and a fluid
line 346. Solenoid 332C is fed hydraulic fluid through the mode
valves 254, 256 from fluid line 152 (i.e. by the drive oil and
therefore can only be pressurized when the mode valves 254, 256 are
positioned in the Drive arrangement). Fluid line 346 delivers
hydraulic fluid from the solenoid 332C to the shift actuator
330C.
Solenoid 332D is in communication with fluid line 152 and is
therefore fed hydraulic fluid from line pressure delivered by the
pump 118. Solenoid 332D communicates the hydraulic fluid to the
shift actuator 330D via a fluid line 348.
Solenoid 332E is in communication with fluid line 152 and is
therefore fed hydraulic fluid from line pressure delivered by the
pump 118. Solenoid 332E communicates the hydraulic fluid to the
shift area 330Ea via a fluid line 350.
Solenoid 332F is in communication with fluid line 152 and is
therefore fed hydraulic fluid from line pressure delivered by the
pump 118. Solenoid 332F communicates the hydraulic fluid to the
shift area 330Eb via a fluid line 352.
Each of the shift actuators 330A-C is fed lubrication oil via fluid
line 224. Each of the solenoids 332A-F and the shift actuators
330D-E exhaust through fluid line 140. A safety valve 360 in
communication with fluid line 140 is set at a predetermined
pressure to regulate the pressure of the hydraulic fluid within the
fluid line 140. This ensures that the clutch control circuits
remain full when not being used to minimize response time. Fluid
line 140 is fed by feed limit pressure oil. Each of the solenoids
332A-F are chosen as either normally closed or normally open so
that a single default gear can be attained in the case of
electrical power loss. For example, if a sixth gear ratio is
desired as the default forward speed during a power loss, solenoids
332A-C are chosen to be normally open and solenoids 332D-F are
chosen to be normally closed.
In addition, each of the fluid lines 336, 342, 346, 348, 350, and
352 that feed the shift actuators 330A-F include an orifice 354
disposed in parallel with a one way valve 356. The orientation of
the one-way valve 356 is such that the one way valve 356 allows
communication from the clutch actuators 330A-E to the solenoids
332A-F and prevents fluid communication from the solenoids 332A-F
to the shift actuators 330A-E. This arrangement forces oil feeding
the shift actuators 330A-E to be controlled through the orifices
354.
An example of specific solenoid engagement and torque converter
clutch engagement is indicated below in Table 1:
TABLE-US-00001 Solenoids TCC Lube Steady State 244 246 242 240 On?
Override? Park 0 0 1 0 No No Reverse 1 1 0 0 No No Neutral 0 0 0 1
No Yes Drive w/ TCC 0 1 0 0 Yes No Drive w/ TCC 0 1 0 1 Yes Yes
Drive w/o TCC 1 0 0 0 No No
A "0" indicates the solenoid is closed and a "1" indicates the
solenoid is open.
A failure mode control is achieved using the first and second mode
valve assemblies 254, 256 and the latch valve assembly 252. For
example, if a Reverse is commanded by the operator of the motor
vehicle, both valves 254 and 256 are stroked. With both the first
and second mode valve assemblies 254, 256 stroked, a flow of
pressurized hydraulic fluid at line pressure from fluid line 152
(which communicates directly with the pressure regulator subsystem
102) is sent through the valves 254, 256 creating pressure in a
Reverse circuit. The Reverse circuit is defined as fluid lines 284,
286, 290, 334, and 336 which feeds shift actuator 330A. In the
Reverse mode of operation, the flow of hydraulic fluid also acts on
a signal end of the first mode valve assembly 254 via fluid line
290 and port 254H. Therefore, if there is a loss of electrical
power, the second mode valve assembly 256 will de-stroke first.
This avoids a potential for the hydraulic fluid to divert to a
Drive circuit, described below, during a Reverse command. The flow
of hydraulic fluid through the Reverse circuit is also used to feed
solenoid 332A in order to avoid Reverse if the solenoid 332A fails
"on" or open in Neutral.
During a Drive command from the operator of the motor vehicle,
pressurized hydraulic fluid must be delivered to solenoids 332B and
332C in order to engage shift actuators 330B and 330C. Accordingly,
the hydraulic control system 100 defines two drive circuits that
both provide pressurized hydraulic fluid to the solenoids 332B and
332C. When the first mode valve assembly 254 is in a de-stroked
position and the second mode valve assembly 256 is in a stroked
position (illustrated in FIG. 1C), hydraulic fluid at line pressure
from fluid line 152 is routed to a Drive01 circuit. The Drive 01
circuit is defined as fluid lines 282, 311, and 340 which feeds
solenoids 332B and 332C. When the first mode valve assembly 254 is
in the stroked position and the second mode valve assembly 256 is
in the de-stroked position, hydraulic fluid at line pressure from
fluid line 152 is routed to a Drive10 circuit. The Drive10 circuit
is defined as fluid lines 286, 302, and 340 which feeds solenoids
332B and 332C. Both Drive01 and Drive10 oils combine into a Drive
circuit by way of the three-way valve 344. The Drive circuit is
therefore defined by fluid lines 340, 334, 336, and 342. The ball
check valve 344 prevents backflow into either of the Drive01 or
Drive10 circuits when one is pressurized with hydraulic fluid. The
Drive circuit is used to feed clutches that are only on while the
driver is requesting Drive and also feed the shift actuator 330A
through ball check valve 338. This is to avoid unintended powerflow
if a Drive-only clutch solenoid 332B and 332C were to fail on in
Neutral.
The two separate Drive oil circuits, Drive01 and Drive10 are
created to allow Drive operation of the vehicle if any one of the
solenoids 244, 246, the first and second mode vale assemblies 254,
256, or the latch disable valve assembly 252 have failed. The
Drive01 oil only feeds the solenoid 186 to avoid solenoid 186
failing to high pressure and resulting in the engine stalling at
low vehicle speeds by engaging the torque converter clutch 189.
This condition can be avoided by detecting the failure and
commanding the Drive10 state so that solenoid 186 is not fed with
pressurized oil.
Upon electrical power failure, it is desirable for the hydraulic
system 100 to latch in a Drive state if the driver was requesting
Drive when the failure occurred. The driver can exit Drive by
either shutting off the engine or select a range other than Drive,
during which the Engine Control Module (ECM) will turn the engine
off. Both actions result in a Park state. The Drive latch is
accomplished by routing pressurized hydraulic fluid via a Latch
circuit to the signal end of the second mode valve assembly 256
when the first mode valve assembly 254 is in a de-stroked position
and the second mode valve assembly 256 is in a stroked position.
The Latch circuit is fed pressurized hydraulic fluid from the feed
limit valve 154 via fluid line 136 and is defined by fluid lines
288, 306, and 308 which communicate the hydraulic fluid to port
256N. The ball-check valve 320 prevents fluid backfill into fluid
line 301. The Latch circuit keeps the second mode valve assembly
256 in a stroked state even if the normally-low solenoids 246 or
244 lose electrical power. If the pressure in the Latch circuit is
not established when electrical power is lost, the first and second
mode valves 254, 256 return to their de-stroked states and the
hydraulic system 100 provides a Park state.
The Latch Disable Valve assembly 252 provides a means to force the
second mode valve assembly 256 to its de-stroked state when the
Latch circuit is pressurized and hydraulic fluid is acting on the
signal end of the second mode valve assembly 256 via port 256N.
This is desirable when commanding a shift from Drive to Park or
Drive to Neutral. In order to override the Latch circuit, solenoid
246 is commanded off or closed and the Latch Disable Valve assembly
252 moves to its de-stroked state. This connects an out-of-Park
(OOP) circuit and a return-to-Park (RTP) circuit to the spring end
of the second mode valve assembly 256 via fluid port 256B. The OOP
circuit is fed pressurized hydraulic fluid from the feed limit
valve 154 via fluid line 136 when solenoid 240 is open. The OOP
circuit is defined by fluid lines 222A, 260, 280, and 300. Ball
check valve 309 prevents fluid backfill into the RTP circuit. The
RTP circuit is fed pressurized hydraulic fluid from the feed limit
valve 154 via fluid line 136 when solenoid 242 is open. The RTP
circuit is defined by fluid lines 266, 280, and 300. Ball check
valve 309 prevents fluid backfill into the OOP circuit. In Neutral,
OOP oil is pressurized by solenoid 240. In Park, RTP Oil is
pressurized by solenoid 242. Either one of these pressurized oils
will force the second mode valve assembly 256 to its de-stroked
state with the help of the spring overcoming the pressure of
hydraulic fluid within the Latch circuit. This returns the first
and second mode valve assemblies 254, 256 to their normal state in
Park or Neutral.
Two circuits pressurize an ETRS Latch circuit that communicates
with a signal area via port 250C on the ETRS valve assembly 250.
The ETRS Latch circuit includes fluid line 262. The pressurized
hydraulic fluid from the Drive01 circuit and the Reverse circuit
communicates from fluid line 340 and 284, respectively, to a ball
check valve assembly 400. The ball check valve 400 includes three
ports 400A-C. Port 400A communicates with fluid line 340. Port 400B
communicates with fluid line 284. Port 400C communicates with fluid
line 262 and therefore the signal end of the ETRS valve 250 via
port 250C. The ball check valve 400 closes off whichever of the
ports 400A and 400B that is delivering the lower hydraulic pressure
and provides communication between whichever of the ports 400A and
400B having or delivering the higher hydraulic pressure and the
outlet port 400C. This pressurized hydraulic fluid from fluid line
340 or line 284 assures the ETRS valve assembly 250 remains in the
Drive state even during failure of solenoid 240. This ETRS Latch
circuit is pressurized when the hydraulic control system is either
in Drive or Reverse. When the hydraulic control system 100 latches
into Drive when electrical power is lost in Drive, the pressurized
hydraulic fluid acting on the ETRS valve assembly 250 via the ETRS
Latch circuit keeps the hydraulic control system 100 from moving to
a Park state. Once the engine is shut off, the loss of hydraulic
pressure within the hydraulic control system 100 sends the
hydraulic control system 100 back into a Park state.
The description of the invention is merely exemplary in nature and
variations that do not depart from the general essence of the
invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *